1. Field of the Invention
The present invention relates to a novel cerium (IV) compound, to a process for the preparation thereof, and, more especially, to a novel cerium (IV) compound directly dispersible in water.
2. Description of the Prior Art
It is known to this art, from Kirk-Othmer, Encyclopedia of Chemical Technology, Second Edition, Vol. 4, p. 850, that it is possible to prepare a hydrated ceric dioxide of the formula CeO.sub.2. .times.H.sub.2 O, wherein x is a number ranging from 0.5 to 2, the compound being present in the form of a gelatinous precipitate, by the addition of ammonium or sodium hydroxide to solutions of ceric salts.
French Patent No. 2,482,075 describes preparation of a cerium (IV) compound dispersible in water by dispersing an essentially dry hydrate of cerium (IV) oxide in an aqueous medium, said oxide having been heat treated at a temperature of from 200.degree. C. to 450.degree. C. in the presence of a deaggregating agent, in particular nitric acid. Heating in the presence of the deaggregating agent effects disintegration of the aggregate crystallites in the hydrate of the cerium (IV) oxide, thereby producing a dispersible cerium compound.
It is noted in the .varies.075 patent that the preparation of the hydrate of cerium (IV) oxide may be by precipitation from a cerium salt; thus, for example, a high purity cerous carbonate may be dissolved in a solution of nitric or hydrochloric acid to provide a neutral solution of cerous nitrate or chloride, which is oxidized with NH.sub.4 OH/H.sub.2 O.sub.2 to produce the hydrate of cerium (IV) oxide.